Winter Project - Titan LSD project

[CtrMint]

I finally managed to test drive my 420R with the new Titan LSD today.  I have to say, there's a big improvement.

Of course there's still noise from the diff given where and how it's mounted.  However, the awful knocks, clonks and low speed maneuvering sounds are pretty much gone.  It's significantly better, basically completely reasonable given the Seven's construction, so much so I wouldn't feel any need to provide feedback to CC, and also don't feel embarrassed if pedestrians hear the Seven being maneuvered.  I reversed full lock numerous times, a process which used to make the car sound like a bag of bolts, even with +40 ft/lb break away etc.  The on/off load clonk is pretty much non-existent, yes its there, but significantly better compared to the original out of the box.

What is really interesting, this diff is quieter than the original I received and drove from the outset.  My first diff was never this quiet.  The response, they all do that, is for me to some degree questionable.  Yes they do, but if the volume on my original was 9/10 from the start, the new one is say a 3/10.  So there's clearly a sliding scale here.  

My testing today also contained more extreme use than the 420R has ever seen, certainly with respect to the diff.  I took the 420R out on ZZR tyres in wet/damp conditions.  I was able to light the rears up in 1st and 2nd gear, the rear felt great, completely consistent in terms of movement at the rear when the tyres were expectedly overwhelmed with my throttle input.   Huge fun too.

As a recap, 

• I dismantled the rear, and rebuilt everything from the prop back.
• All new hardware, nuts, bolts, washers etc.
• Diff shimming was slightly different, I used more of the super thin ones.
• I added additional (externally sourced) super thin shims between the A frame to improve the balance, CC supplied hardware resulted in a slight offset.
• I reused the original diff carrier, two new carriers just wouldn't fit, no idea why!
• Fitted a new handbrake cable.
• Used the Motul diff oil.
• I didn't fit the gearbox spacer, after speaking with CC they advised its use where contact between the gearbox and chassis occurs.  They suggested there was no evidence it improved the diff noise.  I have purchased the spacer, so might fit out of curiosity.

I also changed the gearbox to Redline MTL, while difficult to say for sure, I do think its improved the shift.

I suspect people are going to suggest that it won't last, and I get that.  I'll need to check the preload next, and see where it's at.

 

[CtrMint]

One other observation.  When I used to reverse the 420R, along with the awful noises, I used have this odd and very slight sense the diff was oval in action, or the suspension would lift, which it didn't.  Daft I know.  The same feeling didn't exist driving forwards.  I'd previously checked everything was tight multiple times etc, but never found an explanation. 

Anyhow, I did multiple tests today in reverse (neighbours must had thought I was mad) and that sensation is gone.   Better diff? or have I corrected a build issue from my original work....

[GulfSeven]

Good news its fixed. Your original symptoms weren't at all familiar to me having taken delivery of a 310R with LSD in 2020. The only issue I had was a creak when changing gear after a diff carrier bolt came loose. After tightening it was quiet again.

[CtrMint]

Interesting you say, fixed.  I never really considered mine as a failure, and certainly the advice from CC and their dealer network suggests TADT, and that mine was fine.  

While the diff had slightly increased in noise after the 500miles we did this year in the UK (Taffia) there was no evidence it had actually failed.  My project was more preventative and also convenience, providing a spare facilitating a leisurely rebuild of the original.  I also wanted to gain a better understanding of the diffs behaviour and potential rebuild process.  Based on my sample set, which I appreciate is only 2, there's certainly a notable variance between the two I've been supplied.

[David_Long]

I'm glad it all went well. Quality control can be an issue with Caterhams, so I am not surprised that you efforts have improved it. I really am one for encouraging people not be scared off doing major work.  Once you lose your fear of the unknown, you learn so much, and often quite daunting problems are resolved easily.  

[CtrMint]

I hear you David.

Mind, I still can't get my steering as good as the 620R factory build, but I'm going to pursue that until it's as good as perfect. 

 

[GulfSeven]

Interesting you say, fixed.  I never really considered mine as a failure, and certainly the advice from CC and their dealer network suggests TADT, and that mine was fine.

Fixed in the sense that if mine started sounding like yours I'd want it fixed. They don't all do that...

[edo]

This thread hasnt made me wish I had specified an LSD on my car!

[CtrMint]

Tim I see your point.

[CtrMint]

I am left pondering the outcome, with a couple of questions unanswered, but that's not a bad thing, just part of the journey.

• My original diff was significantly noisier, even with a break away torque of over 40ft/lbs.
• Unsure as to why the rear feels significantly better when reversing.
• The diff carrier has been modified since 2018, yet I couldn't fit the new carrier for interference on the boot floor.

Is it possible CC has changed the specification on the diff again?  Given the successful road test, next thing I need to do is check the break away, see what that's reading.

[ScottR400D]

What makes you think the diff cage has changed since 2018? The one on my 2020 diff is identical to the one my 2015 diff. 

I think it's a bit optimistic to believe that CC have 'changed the specification' on the diff and this is why yours seems a lot better. They've always varied from quiet to outrageously noisy and from lasting no time at all to reasonably long. Maybe you've just been lucky? 

The only way you will find out is to see how it goes over time. 

[Benton]

Out of curiosity do Caterham themselves modify the "factory"  diffs supplied with new cars (both BMW and Ford) or are they outsourced to a 3rd party does anyone know?

[Geoff Brown]

Like the 'crate 'engines' I would think that the diffs are modified in house to suit an application.

[ScottR400D]

Someone modifies the casings, I'd be surprised if it's  CC, and someone fits the LSD units. From what I've been told they don't do all of that work but may do some. (Maybe that accounts for some variations) 

Are the engines modified in house? They weren't a few years ago as far as I know and mine came with a copy of the engine builder's invoice for some reason. 

[CtrMint]

Wrt to changes to the diff carrier/cage, email from CC.

The cages were revised a little while ago to improve the strength around the lower legs. This was done by increasing the amount of weld around this area.

[ScottR400D]

That's quite vague IMO. What's 'a little while ago'. We all know they were changed several times up to around 2015 because of failures, is that what they're referring to?

If not it's quite Interesting, I hadn't realised they had an issue with 'strength around the lower legs'. 

[CtrMint]

My email exchange contained additional information which suggested the change was after the delivery of my kit (Oct 2018) and explained the difference in positioning of the lower legs, albeit by a few mm.  Two revised carriers, one on the new diff and a secondary one both had the same dimensions suggesting a consistent revision.

[ScottR400D]

As I said, all very vague but maybe not that surprising. To twist your words, 'constant revision' suggests someone doesn't know what they're doing. 

I'm still unclear about why it should have needed revision in the past few years, 

[Geoff Brown]

ScottR400D #164 - Yes I agree about the diff being modified by a contractor resulting in inconsistencies & the fact that CC as usual would not batch quality assure components from an external source ? 

I will stand corrected but for engines CC have an in house engine bay where as far as I know the engines are modified for whatever car application is applicable. 

CtrMint - A variation on a theme. Second time lucky a 'quite' Titan LSD. No shunts, clunks or whines ?

Unfortunately that situation may not last for too long being a Titan or have CC found a secret formula. I hope though for your sake it does or LSDs could become a very expensive past time.

[CtrMint]

are you suggesting I don't know what I'm doing?

I purchased a new diff, but really struggled to get it spaced and mounted.  I could get 2 out of the 3 mounts in.  I didn't struggle with the new diff using my old carrier.  I measured both carriers using a vernier gauge and found the positioning of the lower mounts were closer in on the new carrier.  I also purchased a second carrier and found the measurements on that carrier to be identical to the carrier which came on the new diff. I also spent an entire day until the 420R trying to get the new carriers in, a total of approx 8 hours.  I assure you it didn't fit.  When I reverted to my original carrier, I had it on the diff, mounted and spaced in well under an hour.

 

[CtrMint]

Geoff,

It's not totally quiet.  But it's a plated diff, mounted under your backside.   However the noise, especially during low speed reversing and maneuvering sounds normal, in fact it's now no more noisy going backwards than forwards.  On and off throttle there is a small knock, but nothing more than I would expect.  Previously that was pretty bad as shown in the video I originally posted when I first built the car and was told TADT.

When I first built my 420R I recall making the comparison to the LSD fitted in the many rally cars I've been a co-driver in, mostly Group N and E spec Evos and Imprezas.  On a road section such diffs on a stripped rally car are pretty noisy, though they are consistent with just the knock as the driveline picks up torque etc or can be graunchy when tight turning etc.  My original 420R diff never sounded like that, but I was assured like everyone else it was proximity etc.  Driving the 420R now sounds as I'd expect.

 

 

[ScottR400D]

#170 No, I'm not commenting on your ability either way. I'm saying that if the cage is under 'constant revision' then whoever is constantly revising it, when neither of the items it connects to are changing (as far as we know?), then the implication is they they don't know what they're doing.

I'm just trying to make sense of what you're saying. You say CC have suggested the bracket has been revised by adding more weld. That wouldn't stop it fitting in the way you have implied the two you bought wouldn't. 

The cage I got with my new diff in 2020 was identical to the one on my old diff from 2015. The original one was actually assembled by Titan during 2014, c/w with, as written on the invoice, the 'new' bracket. It's well known that up until around 2014, the brackets failed quite regularly and there were several updates to it and the diff back plate. I'm not aware of issues since that time and that makes me wonder why they would feel there was a need to revise it.

Having said that, there may have been a bit more weld on the bracket somewhere but, as I've already said, that shouldn't prevent it fitting. I'm also aware of at least 4 others who did exactly as I did in the past 18 months; bought a new open diff with bracket and fitted a SPC LSD, none of them had any trouble fitting the brackets on their new diffs to their cars.

I do see that at some point the cage part number has changed from 30AO60A to 30AO60D but in CC's normal way, there's no telling why, when or what the change was. Maybe its an issue with race cars? It wouldn't be the first time they changed parts and assemblies to cure race car issues that don't benefit most of us and occasionally have a negative effect, as you will know.

At the moment I can only reach the conclusion that the 2 brackets you were sold were incorrect dimensionally, even CC wouldn't knowingly deliberately modify a component so that it no longer fits. Would they? 

 

 

[John Vine]

As an aside, in #167 Mark recorded CC as saying consistent revision rather than constant revision.  I guess consistent could be interpreted as a policy of continuous improvement?

JV

[ScottR400D]

#173 John, you're absolutely right, my mistake. I see now that Mark is suggesting that as both his cages were the same and didn't fit, the change was consistent. 

However, I think my main points still stand.  

[CtrMint]

I've given the entire situation a lot of thought, and I still don't see why I struggled to fit both of the new carriers. As mentioned the lower legs were closer in but nothing more, I think there was just over 4mm difference. The only impact I can see is that the threads are further away when passing the bolt through the chassis etc, thus the impact from any misalignment exaggerated.

When I tried fitting the carriers I tried a couple of approaches.

1. Top bolt in, then secure the bottom; or
2. Secure the bottom two, then lift the diff up to the top bolt and secure the top bolt.

When I used the second approach it became clear I was hitting my boot floor and just couldn't get the diff high enough to insert the top bolt.  This issue just wasn't present with my old carrier.  I actually ended up buying the second carrier at my own cost, all adding to the rather expensive bill.

I do have faith in the person I spoke to at CC, he has been head and shoulders above most so I'm happy to take his comments at face value and trust his feedback.   It was the chap that performed my 620R revisions.  

Unlike the person that comically packaged a 420R top radiator cooling hose in small box and damaged it through stress by bending it back on itself, and is now refusing to acknowledge the damage.  But that's another story.  Another 80 quid down the drain trying to improve faults.......